Process of manufacturing benzoate.



STATES PATENT OFFICE.

EDWIN O. BABSTO W, OF MIDLAND, MICHIGAN, ASSIGNOB TO THE DOW CHEMICAL COI PANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN.

PROCESS OF MANUFACTURING BENZ OATE.

s ecmano of Letters Patent.

No Drawing. Original application filed October 25, 1905, Serial No. 284,402. Divided nled larch 14, 1908. Serial Io. 305,959.

Patented Nov. 9, 1909,

To all whom it may concern:

Be itknown that I, EDWIN O. BARSTOW, a citizen of the United States, resident of Midland, county of Midland, and State of Michigan, have invented a new and useful Improvement in Processes of Manufacturing Benzoates, (Case (3,) of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distingulsh it from other inventions.

My invention relates to'processes of making benzoic acid and benzoates and articularly to the manufacture of calcium nzoate.

The particular subjectrmatter of this invention has been-divided out of a pendin application for U; S. Letters Patent, file October 25, 1905, Serial N 0. 284,402.

' Said invention consists of steps hereinafter fully described and specifically set forth in the claims. I

The following descri ti'on sets forth in detail certain steps em odying my invention, such disclosed steps constituting but one of various ways in which the principle of the invention may beused.

benzoin and other natural gums by sub ation or extraction, such processes involving the treatmentbf the gum simply with heat, or with an alkaline solution to dissolve the benzoic acid, "and the subsequent preci itation by means of a mineral acid. (2) rom'urine and hiippuri'c acid b well-lmown processes. (3) rombenzyl cl ilorid, benzal chlorid or benzo-tri-chlorid,

b the followin processes: (a) From benzyl c orid by oxi ation with hot dilute nitric acid, giving as resultant products benzoic acid and hydrochloric acid: (6) From ben: zal'chlorid as a byroduct in the manufac- 'ture of benz-aldehy i the benzal chlorid bewater under pressure, with lime an ing treated with a solution of, lime. (a)

From benzo tris chlorid by heating w1th water or a solution of caustic soda and whiting.

. My .invention'rela'tes to those of the above- I mentioned methods in which benzoic acid .o'rthe benzoates are manufactured homologues of benzene one side from .chain, and particularly to that method in which calcium benzoate is manufactured from benzyl chlorid, although my improved series .of hydrocarbons. When manufac-[ tured by the old method noted above from benzyl chlorid the old process hasbeen suh ject to the difliculty that the nitric acid; is

and this application an expensive oxidizer and corrosive SO'fllli'r' glass or stoneware ap aratus is r t e process as a who e suitable for commercial purposes; As manufactured by the old method noted'above from benzal chlorid, benzoic acid and the benzoates are obtained as by-products only,

which-is unsatisfactory when the main pur pose sought is the manufacture of benzoicv acid or benzoates. When manufactured by the oldmethod noted above from benzotri-ch1orid, the old. process is subject to the Some of the various methods by which benzoic acid and benzoates have heretofore been manufactured are as follows: (1) From diflicul-ty that the resultant product always contains im ure acids in the form of chlorbenzoic aci s.

uired and] has been ound In the carrying out of my improved proc- -intermediate product to benzoic acid or. -ben'z'oat by means of a compound containin chlorin. However, I may start withthe c orin substitution product and in that case my improved process would consist of only two steps, viz., the conversion of such chlorin substitution product into'an intermediate product and then the oxidation of the latter to a benzoateby means of'the' chlorin-conta'ming compound. .If I should start with the intermediate product, such.

roduct having only one side chain,

as benzyl alcohol or hertz-aldehyde, my procone would then consist'of only one step, viz.,

' then oxidize the latter to a benzoate by means of bleaching powder and lime. It

will be understood, however, that other comounds may be utilized without departing cm the spirit of my invention;

When toluene is chlorinated to the first stage, either benzyl chlorid or a'chlor-toluene is formed and the tendency is for each molecule of the toluene to take one atom of the chlorin before any molecule takes a second atom, this atom of chlorin going into the side chain or methyl radical of the toluene in a great majority of cases, if the conditions under which the chlorination takes place are proper, such'conditions being principally that the chlorination be aided by heat and take place in the sunlight. If the chlorination is efi'ected in the cold and dark, or there be resent any carrier such as iodin or ferric ch orid, the chlorin will tend to go into the ring and not into the side chain. This tendency of each molecule to take u an atom of chlorin before any molecu e takes up its second atom is probably due to the fact that the toluene is more volatile than either benzyl chlorid or chlor-toluene, so

tact with the chlorin than does the part still remaining as a liquid. When the chlorln atom that is taken up goes into the side chain, it forms benzyl chlorid, and when it goes into the ring, as it does in a com aratively few cases, it forms a chlor-to uene. This chlor-toluene will not form a benzoic acid when treated according to my process, so that it will not form an impurity in my resultant product.'. I therefore obtain a benzoate which holds very little ring chlorin, whatever it does'hold being -obtained from those few molecules of toluene which took up two atoms of chlorin, of whichtwo atoms one went into the ring and one into the side chain; because, if both of the-chlorin atoms or all three of them, if some molecules of toluene had taken up three atoms, had gone into the ring, they would not form a benzoic acid at all, or, if they had gone into the itoluene will be chlorinated to the first stage the-manner described above, and by far to the second or third stage, the probabilities would be greatly increased of obtaininga product in which chlorin had entered both the ring andthe side chain of the toluene, and thus result, when the oxidation is effected, in the production of a chlor-.benzoic acid, as noted above.

Another objection to the, chlorination of the toluene to the second stage, viz: to benzal chlorid or to the .third stage,-viz: to benzo-tri-chlorid, is that much more apparatus is required to treat a given amount oftoluene in a given time, which is uneconomical since the chlorination of toluene is at the best a delicate and comparatively expensive operation. Furthermore, the rate of absorption of the chlorin is muchfaster during the first stage of the chlorination than it is during the later stages; also, the loss due to decomposition is not nearlyso great when benzyl chlorid isformed as it "is when benzo-tri-chlorid is formed, due to the fact that the liquid remains in the apparatus less than one-third as long, and also to the fact that under the conditions benzotri-chlorid decomposes .more readily than benzyl chlorid.

My improved process then consists in chlorinating toluene to the first stage, viz.

to benzyl chlorid, converting the latter to benzyl alcohol by heating with a solution o.sodium carbonate or by any other suit able method and then oxidizing the oenzyl alcohol to calcium benzoate by heating it with a solution of bleaching powder and lime, calcium benzoate thus being formed, which crystallizes out upon cooling the so-v lution. Sodium benzoate may be obtained by adding a solution of sodium carbonate to a hot solution of calcium benzoate. If the chlorination has reached the second stage, the benzal chlorid thus formed would be converted into benz-aldehyde and then the latter bxidized to calcium benzoate by heating it with a solution of bleaching powder and lime.

Asa guide in practically working out my process, the following data, illustrating the relative quantities and course of procedure where the specific materials named are employed, 1s furnished: One part of the benzyl alcohol, which is oily in character as is well known, is agitated with threeparts of water to form an emulsion. Such emulsion is thereupon run into a solution of bleaching powder, lime, and water prepared by add ing four parts of the powder, containing 35% of available chlorin, to twenty-five parts of water and then adding one-tenth part of slaked lime. The entire mixture, after stirring is finally heated in a suitable apparatus. whereupon the following reaction takes place The apparatus preferably employed consists of a common cement-lined iron retort provided with a reflux-condenser, an agitator, and direct steam and water connections for regulating the temperature. The preferred temperature is about 95 C.

Bleaching powder or chlorid of lime is made by absorbing chlorin in slaked lime and the oxidizing constituent of bleaching powder may be regarded as having the formula CaOCl However, the latter may be regarded as a mixture in equal molecular proportions of calcium chlorid and calcium hypochlorite, thus:

2oaoc1 ='cac1 +ca oo1 and in this case the calcium hypochlorite would be regarded as the active oxidizing constituent. In oxidizing a derivative of toluene with bleaching powder it is necessary for practical reasons to have lime present in excess in order to neutralize the benzoic acid as soon as formed, thus keeping the solution always alkaline. If the solution is allowed to become acid, the hypochlorite is decomposed with liberation of free chlorin and conversion of such hypoohlorite into chlorate and chlorid. Obviously a relatively poor yield of benzoic acid will thus be obtained. Since ordinary bleaching powder always contains a considerable amount of caustic lime, it is possible to effeet the oxidation of the benzyl alcohol without the addition of a further quantity of lime, but better results can usually be obtained by the use of an additional quantity of the same.

While I prefer to use chlorid of lime as an oxidizing agent, I use other substances of a similar nature containinghypochlorites, in

which the calcium'is replaced by some other metal. Such substances may be obtained by absorbing chlorin in alkaline earth hydrates either in solution or in the solid state. Furthermore, hypochloritecontaining substances having similar properties may be obtained by absorbing chlorin in alkaline hydrates either in solution or in the solid state, and in connection with such a method I wish particularly to refer to my pendingapplication for U. S. Letters Patent, Serial No. 305,958, filed March 14, 1906. Asan examule of the foregoing,

.zoate.

sodium hypochlorite is obtained, which is an active oxidizing agent, when chlorin is absorbed in .a solution of sodium hydrate, thus:

.the oxidation to benzoates, by means of bleaching' powder or. similar hypochloritecontaining substances, of benzyl alcohol, benz-aldehyde or similar side-chain derivatives of the homologues of benzene, such derivatives being oxygen containing oxidation products intermediate of the chlorin deriva tives of such homologues and the benzoate being formed. These intermediate products which require oxidation to form benzoic acid are obtained from the chlorin derivatives of members of the benzene series of hydrocarbons in any suitable manner. Q 7

It will be noted that while I prefer to stop the chlorination of the toluene at the first stage, viz., at the formation of benzyl chlorid, it is not necessaryto do so, but that I can stop at any pointshort of the complete conversion to benzo-tri-chlorid, such chlorinated toluene then'being in the form of a mixture of toluene, benzyl chlorid, benzal chlorid, benzo-tri-chlorid, and small amounts of decomposition products and compounds with chlorin in the ring, this mixture, upon being treated with a solution of bleaching powder and lime, being oxidized directly to calcium benzoate without further chlorination, which further chlorination would ive a product yielding a less pure calcium n- In this process I convert the chlorin derivatives of toluene into intermediate products and then oxidize the latter to benzoates, as, for instance, converting benzal chlorid to benz-aldehyde by heating with a solution of lime and then oxidizing the benzaldehyde to calcium benzoate by heating with a solution of lime and bleaching powder; yet, I might oxidize the chlorin derivatives of toluene directly to calcium benzoate by heating with a solution of lime and bleaching powder, or by heating with a solution of sodium hydrate and sodium hypochlorite, respectively, and, in this connection, I refer to my pending applications for U. S. Letters Patent mentioned hereinbefore, viz., Serial No. 284,402, and filed October 25, 1905 and Serial No. 305,958, filed March 14, 1906.

Benzo-trichldrid does not require any oxidation to form benzoic aci and hence my process is not applicable th reto. By my improved process I obtain a substantially pure benzoic acid, due to the small percentage of chlorinated toluene which contains its chlorin both in the side chain and in the ring; furthermore, in order to obtain a given amount of benzoates, I require less than onethird of the apparatus and only one-third of the amount of chlorin gas that has been necessary heretofore when the toluene was converted into benzo-tri-chlorid, the remaining oxidation being effected by means of chlorid of lime which is easily and cheaply made by absorbing chlorin in slaked lime.

Having thus described my invention in detail, that which I particularly point out and distinctly claim is:

1. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a partially oxidized oxygen-containing product of a member of the benzene series of hydrocarbons by means of a chlorincontaining reagent in the presence of a basic neutralizing reagent and a suitable solvent.

2. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a partially oxidized oxygen-containing product ofamember of the benzene series of hydrocarbons by means of a chlorincontaining reagent in the presence of an alkaline earth hydrate and a suitable solvent.

3. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a partially oxidized oxygen-containing product of a member of the benzene series of hydrocarbons by means of a chlorincontaining reagent in the presence of lime and water.

4. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a partially oxidized oxygen-containing product of a member of the benzene series of hydrocarbons by means of bleaching powder in the presence'of a suitable solvent, such .bleaching powder containing sufficient lime to neutralize the acid formed by the reaction. 1

5. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a partially, oxidized oxygen-containing product of a member ofthe benzene series of hydrocarbons by means of bleaching powder in the presence of Water and of lime in excess of that contained in said bleaching powder.

6. In a process of manufacturing benzoates, the step which consists in oxidizing benzyl alcohol to the acid by means of a chlorin-containing reagent in the presence of a basic neutralizing reagent and a suitable solvent.

7. In a process of manufacturing benzoates, the step which consists in oxidizing benzyl alcohol to the acid by means of a chlorin-containing reagent in the presence of an alkaline earth hydrate and a suitable solvent.

8. In a process of manufacturing benzoates, the step which consists in oxidizing benzyl alcohol to the acid by means of a chloriu-containing reagent in the presence of lime and water.

9. In a process of manufacturing benzoates, the step which consists in oxidizing benzyl alcohol to the acid by means of bleaching powder in the presence of a suitable solvent, such bleaching powder containing sufficient lime to neutralize the acid formed by the reaction.

10. In a process of manufacturing benzoates, the step which consists in oxidizing benzyl alcohol to the acid by means of bleaching powder inthe presence of water and lime in excess of that contained in said bleaching powder.

11. The process of manufacturing benzoates, which consists in forming an emulsion of benzyl alcohol with water, mixing such emulsion with a solution of bleaching powder to which has been added a quantity of slaked lime, and thereupon heating.

Signed by me this tenth day of March,

EDI/VINO. BARSTOW. Attested by WM. L. BAKER, Eow. A. LANE. 

